1. Field of the Invention
This disclosure relates generally to access covers for septic tanks and generally vertical access passageways between a septic tank (or another underground on-site waste disposal system or drainage collection system component) and grade level, and more specifically, to a component for use with (or without) a passageway formed by multiple stackable riser members, which component is capable of being cast into a concrete septic tank top, as well as being stackable with one or more riser members, and removably accepting a concrete or other heavy material cover or inspection lid therein, as well as being adapted to removably accept another cover thereon.
2. Description of the Prior Art
An important consideration in the construction of septic tanks and other underground waste or drainage systems is how to provide water tight access to the buried system components for purposes of periodic maintenance (such as for pumping out a septic tank, which is typically done at least every few years, and in some cases, annually or even more frequently). Often, septic tanks and other underground liquid waste-holding components are provided with precast concrete covers, preferably with lift handles cast therein, in order to gain access to the interior of the septic tank. The concrete cover is typically located in the concrete top section, or lid, of the septic tank.
There have been problems related to the use of make-shift access passage assemblies, such as modified chimney flues made of clay tile or cement, or extended lengths of large diameter pipe (such as smooth-walled PVC pipe, or corrugated or co-extruded pipe), used to form passageways between septic tanks and grade level. In order to overcome problems associated with such make-shift assemblies, a favorable alternative has been developed in the form of durable stackable riser members, as typified by the riser members disclosed in U.S. Pat. Nos. 5,617,679 and 5,852,901, owned by Tuf-Tite, Inc., the assignee of the present invention. Such riser members are typically made of comparatively lightweight, but sturdy material, such as polyethelene. Such injection-molded stackable risers allow for easy adjustment of the overall height of the access passageway, since additional risers can be easily added to increase the height, or risers can be removed to shorten the passageway. In a preferred manner of using these stackable riser members in conjunction with concrete septic tanks, the lowermost riser member is cast directly into the concrete top of the septic tank form. In this manner, perpendicularity of the entire access passageway, formed by a stack of risers, to the top of the septic tank is reliably established and maintained.
As disclosed in U.S. Pat. No. 5,852,901, the riser members can be interconnected by means of a generally inverted U-shaped connecting member or channel provided at a lower end of the riser member, which is adapted to receive a free upper end of a next-lower riser member in a given stack of risers.
It is recognized that later-developed riser members, such as the stackable riser sold by Polylok, Inc. and United Concrete Products, Inc. of Yalesville, Conn., employ variations of technique of interconnection of the riser members disclosed in U.S. Pat. No. 5,852,901. For example, as described in U.S. Pat. No. 6,484,451, the risers employ a channel end and an opposite tapered or straight end. The channel end of the riser member includes a middle wall, with notches or slots at regular intervals therein, defining two concentric channels. In a cylindrical stackable riser of the type disclosed in that patent, the middle wall is essentially an interrupted ring. The outermost channel receives the tapered or straight end of the next-lower stackable riser member, and the inner channel of the channel end, together with the notches in the middle wall of the channel end, receive vertical reinforcing ribs provided on the interior wall of the next-lower stackable riser member.
Access passageways formed by stackable risers, such as those described in U.S. Pat. No. 5,852,901 of Tuf-Tite, Inc., are known to be used in conjunction with an injection molded cover used at grade level. The injection molded cover can terminate a stack of risers by being placed on the uppermost riser in the same manner of interconnection as the other risers, e.g. by an inverted U-shaped channel extending downwardly from the cover.
The cover is secured to the uppermost riser by, for example, securement screws and screws which extend vertically through the cover at its perimeter, and which are received in screw bosses provided around the exterior of the uppermost riser in a stack of risers, all for safety and security reasons. Such covers are preferably provided with additional horizontally-oriented securement screws, screws, or other fasteners, which extend in a direction perpendicular to the vertically-extending securement screws. Instead of being received in screw bosses, these lateral securement screws may abut the upper lip of the uppermost riser which is received in a channel provided in the bottom of the cover, or alternatively, extend through screw holes provided in the upper lip of the uppermost riser in a stack of risers. Even with such securement methods available for the injection-molded covers, there exists a need for an additional cover in the form of a heavy-duty concrete (or other heavy material) secondary cover provided either just below the injection molded cover, i.e. at or near grade level, or alternatively, in or immediately adjacent to the concrete lid of the septic tank, i.e. at or near the bottom of the passageway.
Those of ordinary skill in the art will understand that the term “concrete lid” of the septic tank refers to the large, horizontally-oriented concrete slab, typically on the order of 4 feet by 8 feet, for example, provided at the top of the septic tank having a capacity from about 750 to about 1,250 gallons, and supported by the walls of the septic tank, as opposed to the term “concrete cover”, which as used herein, refers to the well-known removable, generally smaller (and typically round) cover member associated with an opening in the concrete lid and used to gain access to the interior of the septic tank. Such concrete covers are generally flat, have cylindrically-shaped outer peripheral walls, while others may be tapered, and may include a stepped portion. The concrete covers sit atop the concrete lid, over the lid's access opening. These concrete covers allow a point of access to the interior of the septic tanks for drainage, cleaning, or other maintenance, including access to effluent filters provided at the inlet or outlet of the septic tank, for cleaning or replacement of the filters. Even in instances where a covered access passageway is provided over the concrete lid of the septic tank, there is a growing need for such secondary concrete or other heavy material covers over the lid's access opening in order to comply with many existing and imminent state and local regulations requiring such covers, as well as for added safety considerations. In those localities where there are no regulations requiring covers of a particular material or weight, it is still beneficial to use an internal cover within a septic tank or other on-site waste system access passageway, even if the cover is made of a lightweight material, such as plastic.
It is recognized that conventional on-site waste system access passageways formed of extended lengths of PVC pipe have been outfitted with plastic or fiberglass covers, often secured to the top of the PVC pipe by screws. However, such arrangements are considered even less secure than the stackable risers with injection-molded covers. Further, the PVC pipe passageways, which typically have smooth inner walls, do not provide any means for accepting and retaining secondary concrete or other heavy material septic tank covers, either at or near grade level, or lower down in the passageway.
One difficulty relating to the use of concrete covers in the lid of the septic tank, especially in combination with such passageways formed by stackable risers, occurs when the concrete cover is cast in place in the concrete lid of the septic tank. Such covers are typically formed in a steel forming pan used repeatedly by a concrete pre-caster, for the sole purpose of casting concrete covers. The installer has little room in which to cast the lowermost riser in place around the pre-cast concrete cover. Due to such space considerations, the casting of a concrete lid for a septic tank with a cast-in lowermost riser is often achieved using several separate pouring operations. First, a lowermost riser is placed on the floor and a steel pan is placed therein. Next, concrete is poured in the space between the outside of the steel pan and the inside of the lowermost riser. After that, concrete is introduced into the inside of the steel pan to form the concrete cover. The steel pan is often frustro-conical in shape, with a lower end having a smaller diameter than the upper end. Before the concrete cover dries, it is desirable to add a cast-in handle, such as the H1 “Cast In Handle” available from the present assignee, Tuf-Tite, Inc., i.e. to the center of the concrete cover to facilitate removal and replacement of the cover. Finally, concrete can be poured to form the concrete lid of the septic tank around the outside of the lowermost riser, thereby encasing and retaining the lowermost riser within that concrete lid.
The concrete cover is removed from the ring of concrete formed in the interior of the lowermost cast-in-place riser, and the steel pan is removed for re-use. Due to the frustro-conical shape of the pan, once the steel pan is removed, the resulting concrete cover has a frustro-conical profile which can then be placed over the complementary concrete ring formed in the interior of the lowermost stackable riser, which serves as a mating angled seat for the concrete cover. There is a tendency for there to be a mis-matched fit, which results in a locking wedge fit between the concrete cover and the complementary concrete ring, which is undesirable.
At least one such stackable riser, such as is available from Tuf-Tite, Inc., includes an interiorly-extending annular ring, which provides some internal support for the concrete interior ring. However, due to the relatively narrow width of the concrete ring within the concrete riser, there is some concern about degradation of the concrete seat for the concrete cover. Over the years, repeated access to the septic tank via the concrete cover may tend to cause chips or cracks in the concrete seat, particularly if people accessing the tank drop the concrete cover in place from any significant height above the top of the septic tank, as is not uncommon due to both the weight of the concrete cover and the depth of some septic tanks.
It would be desirable if the lowermost, cast-in-place riser could also form the mold pan for the concrete cover and also remain in place as the seat for the concrete cover when the concrete septic tank lid is installed underground on a septic tank. This approach would advantageously avoid the need for a separate steel form pan, reduce the number of pouring operations during casting, and add reliability to the resulting seat for the concrete cover. The manner in which these and other benefits of the present invention are achieved will be explained in greater detail in the following Detailed Description of the Invention and the drawings.